Thematic Mapping Techniques Questions and Answers

Answer: C

Selecting the scheme for its effect rather than its fit to the distribution shapes the conclusion before the reader arrives. The defensible approach is to choose on the shape of the data and to state which scheme was used.

Answer: D

Provenance and currency decide what weight a pattern deserves, and a reader cannot assess either from the sheet alone. It is a matter of accountability rather than of decoration, and a map that omits both is asking to be believed on trust.

Answer: A

Correct answer: taller units hide the ones behind them

Raising the units into prisms puts them in front of one another, so a tall unit occludes whatever lies behind it from the chosen viewpoint. Values in the obscured units cannot be read at all, and the map must be rotated or re-drawn to reveal them. The technique also makes heights hard to compare across the sheet because of perspective, which is why it is more often decorative than analytical.

Answer: B

Correct answer: keeps the units joined to their neighbours

Both types resize the units by the mapped value; the difference is what is sacrificed to do it. A contiguous cartogram keeps the units joined and distorts their shapes to make the areas fit, so the map remains a connected whole but individual outlines become unrecognisable. A non-contiguous one keeps each shape true and lets the units float apart, so the topology is lost instead.

Answer: C

Correct answer: True

The Dorling cartogram abandons shape altogether: each unit becomes a circle whose area is proportional to the value, and the circles are displaced until they no longer overlap while staying as near their true positions as possible. What is gained is an unambiguous encoding of magnitude; what is lost is any sense of the real geography, so the reader must already know the area reasonably well.

Answer: D

The first two are correct, and the second is the standard objection to the technique. The third is wrong: a cartogram already scales by a base such as population, so mapping a raw count on top of it would double-count that effect.

Answer: A

Correct answer: about 1, 1.7 and 2.4

Scaling by area means the radius goes with the square root of the value: \[ \sqrt{1} = 1, \qquad \sqrt{3} = 1.73, \qquad \sqrt{6} = 2.45. \] The 1, 3 and 6 offered is what results from scaling the radius directly by the value, which would make the largest circle 36 times the area of the smallest instead of 6 - the standard error in proportional symbol work, and always in the direction of exaggeration.

Answer: B

A gain of a thousand means something quite different in a village and in a city, and dividing by the starting value puts the two on comparable footing. Where the units start from similar sizes, the absolute difference is easier to read.

Answer: C

Drawing a line through intermediate values presumes those values exist between the observations. Applying the technique to something discrete, such as the location of factories, asserts a continuity the phenomenon does not have.

Answer: D

Correct answer: colouring the bands between contour lines

Layer tinting, or hypsometric tinting, fills the band between successive contours with a colour from an ordered sequence, so height is read from the colour rather than by finding and reading a contour value. The convention runs greens through yellows and browns to white, and it is the reason a small-scale relief map can be understood at a glance.